Automatic telephone system



Sept. 1, 1925. 1,551,773

' A. J. RAY

AUTOMATIC TELEPHONE SYSTEM Filed Sept. 16. 1920 Patented Sept. 1, 1925.

emsen STATES names )3. amigos CHIdAGOyII-ILINOIS, assrenon'ronumomn rr'o EnEoT-R'Io COM- 1,551,123 e swear orries.

iPANYQUF CHICAGO, auzmors, :A: CORPORATION or ILLINOIS.

AUTOMATIC TELEPHONE SYSTEM. 7

"Application filed September 16, 1920. sc -mine. 410,596.

My invention relates in general to-auto-v Inatic telephonessystems, but ino reespeciaL ly tQfitllltQIIlittlC systemsof relatively small size, intended for use in furnishing telephone service between the'various departments of a lar e commercial or manufacturin establlshment. A system of this lnndis common.- iylmown as a private automatic exchange,

or V V V The OlOJBCtS of the lIlVQDlJIOD are-several and may be briefly enumeratedas follows:

To provide an improved final connector switch for use in a system of the above; character, having automatic trunkselecting and impulse repeating functions on one ormore levels and 'referredito .Jhereinafter as a selector connector repeater; to provide a metering arrangement for counting the total number of completed connections in a private automatic exchange; and to;provide.a metering arrangeinent for counting the total number of attempted trunk connections which fail because no idle trunks are available. v

Ut herimprovements not now specifically mentioned are provided also all of which will be described fully hereinafter, reference being-had to the-accompanying drawing.

Referring to the drawing, which co1nprises a single sheet, suflicient apparatus is shown therein to enable the invention to be readily understood. The reference characfor A indicates an automatictelephone substation of theusual type having theusual talking instrumentalities and a-calling ;device S for controlling. the central oilice switches. The line conductors 11 and 12 extend to a central point where the switching mechanism or exchange is located and there te minate in the individual lineor trunk seiecting switch C. The line switch C is of the well known rotary type, with wipers movii in a iorwarddirection only and having no normal position, andfhas=theffunction of ding the line oflsubstation A, when the is einoved 'toa trunk linetermildleselecter. connector. repeater;

C ne of thesetrunk lines which is accessible't'o'the line switch C and other similar linesrvitches is shown inthe drawing and terminates in the selectorconnector rep'eaterintlifcated b'y reference character D. The switch D is of the well "known Stowger type having one hundred contact sets arranged inte'nrows or levels. Thefirst eight levels are reserved for local traffic within the P. AJX. andwhen-worlring ontlrese levels the switch D "has the functions of'an ordinary connector switch. Thetwo 'top levels, or the ninth and tenth'levels, are reserved "for trunk lines. "On these two levels the switch D has the functions of aselector sx'vitcln'tliat is, when raised toeither the ni'nth or'te'nth .level the switch will operate to sele'ct an idle trunkline automatically. The trunk lines terminating" inone level,- say thetenth, extend'to. another private auton' 'atic exchange, andon this level the switch "D has the functions of anautomatic impulse repeater. r I 1 i The arrangement of the difltereiit'b'ank levels may be'better understoodfrom a more detailed consideration of the situation in whichthe 'P. A. X. is used. It isassumed thatthe concern usingthe 'P. A. X has two factories-or other establishments located a; short "distance apart in a city served'by a public inanualexchange. One of the factories'is supplied withtelephone service by the A. K. under discussion, while 'the other-factory is supplied witlrtelephone service by another private automatic exchange of theysaine type. The tenth level in the selector connector repeaters in'the 'P. A. X. at factory No. 1 is -reser 'ed for tl'1efprivate trunk lines extending to the P. A. XJat'factory No. 2, while the ninth level is used for iii) trunk lines extending ilOjtllGiPllbllC manual ing in the ninth level and extending to the public manual exchange, where the trunk line may terminate in an ordinary drop and jack, It is understood that there are or may be a plurality of trunk lines in each of the ninth and tenth levels similar to the ones described.

The operation of the system may now be described, it being assumed first that the subscriber at substation A desires to obtain connection with the subscriber at substation A.

lVhen the receiver is removed at substation A a circuit is completed over the line conductors 11 and 12 for the line relay 15 of the line switch C. Upon energizing, the line relay 15 closes at its armature 21 a circuit which includes the switching relay 1a and the stepping magnet 16 in series, and at its armature 20 connects the test wiper 2% to the above circuit at a point midway be tween the switching relay and the said magnet. The operation now depends upon whether the trunk line with which the wipers of the line switch C are associated, is busy or is not busy. If the trunk line is busy the test contact with which the test wiper is in engagement will be grounded, and as a result the switching relay 1%; will be short circuited and the stepping magnet 16, being supplied with direct ground by way of the test wiper, will operate as a buzzer to ad vance the switch wipers step by step in search of an idle trunk line. It may be assumed, however, that when the call is initiated the wipers of the line switch C are standing upon the bank contacts shown in the drawing, and it may be assumed furthermore that the trunk line extending from these bank contacts is idle. Under these circumstances the test contact 28 will have no ground potential upon it and when the receiver is removed the energization of the line relay 15 is followed immediately by the energization of the switching relay 14:. It may be stated at this point that the switching rclay is of very high resistance so as to prevent the operation of the stepping magnet 16 at this time. As a result of the energization of the switching relay 14 the line conductors 11 and 12 are disconnected from the line relay 15 and from ground, respectively, and are extended by way of armatures 17 and 19, wipers 22 and 25, and bank contacts 26 and 29 to the upper and lower windings of the double wound line relay 50 of the selector connector repeater D.

lVhen the calling line is extended to the switch D as above described, the line relay 50 is energized over the line circuit in the usual manner and completes a circuit for the slow acting release relay 51. Upon energizing, the latter relay prepares a circuit for the vertical magnet 60 at armature 75, and at armature 77 connects ground to the release trunk conductor 76, thereby closing a holding circuit for the line switch C which extends by way of the test contact 28, test wiper 2 1 armature 18 and its working contact, winding of the switching relay 14, and the winding of the stepping magnet 16 to battery. The above circuit is completed before the slow-acting line relay 15 has had time to deenergizc and serves to maintain the switching relay 1 1 energized throughout the connection. Ground is also extended by way of the private normal conductor 95 to multiply connected test contacts in the banks of the selector connector repeaters which have access to the line of substation A, whereby the said line is made busy.

The calling subscriber at substation A may now proceed to operate his calling device S in accordance with the digits in the local telephone number of substation A. When the calling device is operated for the first digit a series of interruptions is produced in the line circuit, to which the line relay 50 responds by deenergizing a corresponding plurality of times. At each deenergization the line relay transmits a current impulse to the vertical magnet 60 over the following path: Ground at G armature 7A and its resting contact, armature T5 and its working contact, off normal springs 63 and 65, winding of the slow acting series relay 52, winding of the vertical magnet 60, and the winding of the common relay 103 to battery. The above is the circuit over which the first impulse is transmitted. At the first upward movement of the shaft the normal springs are shifted and the circuit is completed over a new path which is the same as the one previously traced except that it includes the off normal springs (53 and (i l and armature 81 of the series relay 52 and its working contact, the said series relay being now in operated position. By the operation of the vertical magnet 60 the wipers 130-132, inclusive, are raised step by step until they stand opposite the level of bank contacts in which is located the set of contacts associated with the line of substation A. The slow acting series relay 52, which is energized in series with the vertical magnet, maintains its armatures attracted throughout the vertical operation of the switch, and at the end of the vertical movement deenergizes and transfers the operating circuit to the rotary magnet 61.

The calling subscriber may now operate his calling device in accordance with the second and final digit in the desired number. As before, a series of interruptions is produced in the line circuit to which the line relay 50 again responds by transmitting a series of impulses to the rotary magnet 61 over the following path; Ground at G, armature 7 1 and its resting contact, armature and its working contact, on normal springs 63 and 64, armature-81 and its resting contact, normallyclosed contacts controlled by armature 90 of relay 57, armature 101' and its resting contact, winding of the rotary magnet 61', and the winding of the common relay 103 to: battery. Responsive to these impulses the rotary magnet is, operated to rotate the switch wipers into engagement with the particular set of bank contacts in which the line of substation A terminates, these bank contacts being indicated in the drawing by reference characters 133, 134, and 135,. The slow acting relay 58 is energized in parallel with the rotary mag-- net and remains in operated position while the switch wipers are being rotated; At its armature 91, relay 58connects the test wiper 131 to the winding of the test relay 57, and at its armature 93 relay 58 closes the operating circuit for the rotary magnet over a path which is independent of the contacts controlled by armature 90 of the test relay 5'7. Thislatter operation is to guard against the possibility of the test relay being energized while the test wiper 181 is passing over busy test contacts. Assuming first, that the line of-substation A is busy-when connec tion thereto is established as just described, when the test wiper 181 comes to rest in engagement with the test contact 134 it will find aground potential thereon and the test relay 57 will be operated. Upon energizing,

the test relay establishes a locking circuit lor itself at its armature 89 and at its armature 94 connects a 'lead'from the busy signalling machine to the lower heavy talking conductor. By this means the calling subscriber is given an audible busy signal, and being advised thereby that the desired line is for the time being inaccessible, he will hang uphis receiver and release the connection.

Having described the operations which take place when the called line is busy, it will now be assumed that the called line is idle when the connection is attempted. Under these circumstances, whenthetest wiper 131 comes to rest in engagement with test contact 184 it will find no ground potential and the test relay 57 will not be energized. when the slow acting relay 58 deenergizes. at the endof the rotary movement of the switch a circuit will be-completed for the switching relay 59 as follows: From the grounded release trunk conductor 76, by way of armature S9 and its resting contact, upper winding of switching relay 59, resting contact of armature 91 and the said armature, normally closed contact springs controlled by armature 98, test wiper 131, test contact134, private normal conductor 143, winding of the switching relay 14", and the Wind-in of the stepping'magnet 16oto battery. pon the closure-of'the above circuit relays 59 and 1 4 I are energized in series, andthe latter relay Thenis operated to clear the lineof substation A of its normalbattery and ground connections in the line switch C. It is noted that relay 14 operates only about half way, due

to the fact that the line relay has not been energized, and the line conductors are not connected through to thewipers of the line switch. At the selector connector repeater D when the switching relay 59 is en ergized the said relay establishes a locking circuit for itself at its armature 99, connects direct ground to the test wiper 131 at armature 98, opens the rotary magnet circuit at armature 101, and at armatures 97 and 100 connects up the line wipers 130 and 132,

The connection having been finally completed, ringing current from the generator Gen is projected intermittently out over the line of substation A in the usual manner to operate the bridged ringer at the substation, It will be understood that the return path for the ringing current includes the upper 'winding of the ring cut oil relay 56 and contacts of these armatures finally completes the talking connection.

The desired connection. has now been established. The transmitter at the calling substation A is supplied with talking battery through the windingsof the line relay 50, while the. transmitter at substation A is supplied with talking battery through the windings of the double wound back bridge impedance coil 54. The voice currents take the path shown inheavy lines which will be understood without further explanation.

When the subscribers are through talking they will both, replace their receivers, and. the replacement of the receiver at substation A causes the line switch C and the selector connector repeater D to be released in the following manner: hen the line circuit is broken by the replacement of the receiver the line and release relays 50 and ,51 are both. deenergized, and a circuit is completed for the release magnet 62 which operates to restore the connector D to normal position in the well understood manner. Relay 51 also disconnects ground from the release trunk conductor 76 thereby permitting the switching relay 14 of the line switch C to deenergize. 'By the deenergization of relay14 the line switch C is restored to normal condition ready for another call. It will be noted that the circuit of the release magnet 62 includes the common relay 1652. Relays 102and 103 repeaters, and have the function of controlling the operation of the meter M which is provided for the purpose of registering the total number of completed connections which are established in the P. A. X. lVhenever the switch D or any other similar switch in the P. A. X. is released, the relay 102 is energized in series with the release magnet and closes a circuit for the operating magnet of the meter M in order to register the connection, providing of course that the relay 103 is not energized at the same time. Under the circumstances just described, when the switch D is released at the termination of a successful connection, relay 103 will not be operated, its circuit being open at armature 101 of relay 59, and the call will be registered on the meter M. But if the switch D should be released prematurely, that is, before it has been completely operated, either the vertical magnet or the rotary magnet 61 will be energized just before the release magnet 62 is energized and it follows there fore that the relay 103 will also be operated. Belay 103 is made slow acting so that it will retain its armature attracted after the circuit of the operating magnet has been broken and until the switch has been completely restored in order to prevent the relay 102 from closing the circuit of the meter operating magnet to register the call. Thus no connection will be registered when the switch is released after being only partially operated.

It will be observed that the operating circuit, or the circuit including relay 103, is opened by the test relay 57 as well as by the switching relay 59, and that meter M will, therefore, register calls to busy lines as well as calls to idle lines. It may be stated that for the purposes of trafiic observation, calls to busy lines are regarded as completed calls, as in fact they are in one sense. The equipment used in a call to a busy line is the same and is used for about the same length of time as the equipment invloved in a call to an idle line, and the purpose of a traflic stuc y being to determine the proportion of equipment to total calls involving such equipment, it is desirable to include calls to busy lines in the total.

The function of relay 103 is principally to prevent a double registration on ordinary answered calls. For instance, when the connection just described is released, relay 102 pulls up and operates the meter M to register the call, as above explained. Yew, if the called subscriber has not yet hung up, as will be the case about fifty per cent of the time, his line switch will operate at once to seize an idle connector; and when the called man finally hangs up, the vertical magnet and the release magnet of such connector will operate successively. Relay 103 energizes in se ries with the vertical magnet and prevents relay 102, which pulls up in series with the release magnet, from operating the meter a second time for the same connection.

Having described the process of setting up a local connection I will now explain the manner in which a trunk connection to the main exchange is established, after which a d'esxription will be given of the process of establishing a trunk connection to a subscriber in the other private automatic exchange which is located at factory No. 2. Before proceeding it will be convenient to explain a little more fully certain details concerning the restricted service feature, particularly with regard to the means for classifying the P. A. X. subscribers in accordance with the class of service to which they are entitled. As before stated, the subscribers are divided into three classes. The subscribers in class No. 1 are given local service only, that is, they can call neither the manual main exchange nor the other private automatic exchange. The subscribers in class No. can establish local connections and also are able to establish trunk connections to the other private automatic exchange, but not to the main exchange. The subscribers in class No. 3 have no restriction imposed on their services and can establish local connection and both kinds of trunk connections. In order to differentiate between the difterent classes of subscribers automatically each individual line switch is provided with an extra wiper and bank of contacts and the trunk line extending to each of the selector connector repeaters is provided with an extra conductor, there being four conductors in each such trunk line. This arrangement is clearly shown in the drawing in which the line switch C is shown as having an extra wiper 23 which has access to the fourth conductors of the several trunk lines extending to the selector con nector repeaters, one of which conductors is the conductor 106. hen used in connection with a restricted service system this fourth conductor is commonly referred to as a dis criminating trunk. The class of service to which any subscriber is entitled is determined by the manner in which the extra wiper of each individual line switch is connected. Three busbars are provided at the line switchboard which may be numbered 1, 2, and 3 as shown in the drawing. Bus-bar No. 3 is permanently connected to ground, bus-bar No. 2 is connected to ground through a resistance of about 500 ohms, while bus-bar No. 1 has no ground connection at all. The extra wipers of the several line switches are connected to these three bus-bars in accordance with the class of service which is to be given to the different subscribers. For ex ample, the extra wiper 23 of line switch C is connected to bus-bar No. 3 and it follows therefore that the subscriber at substation A t ry-magnet at its armature circuit referred to extends to the discrimihating-relay as follows:

belongs-to the third class and is striated service.

The explanation of the manner in which a trunk connection to theinain exchange-is established may now be proceeded with. As before stated, the trunk lines extending to the main exchange terminate in the ninth level. It follows therefore that in order to connect with one of these trunk lines the digit 9 must be called. ihe subscriber at substation A. who desires to connect with the'main exchange will therefore remove his receiver andoperate his calling deviceS in accordance with the digit 9. When the receiver is removed the line switch C operates given unreasbefor'e described to -extend the associated line to a trunk line terminating in an idle selector connector repeater. Assuming that the selector connector repeater D is idle and is selected for use, when connection is exofthe' line relay and are brought to rest opposite th ninth level, all in'the manner previously eXplained. When the wipers are raised 'to' the ninth level the shaft controlled springs and 72 are brought. into engagement with springs 71 and '73. respectively, by the operation of the shaft. This may be ac'complishedby any suitable cam arrangement. A convenient way is to mount the spring assembly comprising springs Gi -73, inclusive. justabov'e the top of the shaft so that springs 68 and 70 may be actuated by the circular cup spring casing which'is mounted at. the upper xtremity of the switch shaft. To proceed, the slow'acting series relay 52 is energized during the vertical operation of the switch and for an instant thereafter, and when the ninth level shaft springs are close'don the ninth vertical step two circuits: are completed which will now be pointed out. The first of these 0' "cuits serves to energize the test'relay 57 and may be traced as follows: From the grounded release trunk conductor 76; by way of resistance 101-, shaft springs 72 and73, rotary oil :norma-lspring 6? and its resting contact, armature 80 and its working contact, interrupter contact '88 of the rotary magnet, and the winding of the test relay 5? to battery. Upon energizing, the test relay 57 looks itself at its armature 89 and prepares a circuit for the re- 90. The second From grounded busebar No. 3 at the line switchboard by wayof conductor 10?, wiper 2-3, bask contact 27, discriminatingtrunk conductor 106,

shaft'springs 71 and 70, armature 79 and its working contact, resistance 105, and lower winding of relay 53 to battery. rectground is supplied to the discriminating trunk conductor 106,1relay 53 is energizednot-withstanding the fact that resistance 105 is included in this circuit, andestablishes a locking circuit for itselfat arn1at-ure 88. Relay 53 also short circuits resistance 104 at its armature 82.

When the vertical movement of the switch is completed and the slow acting relay 52 is deenergized a circuitis completed for the rotary magnet 61 which extendsasfollows: From the grounded release trunk conductor 76, by way of the workingcontact of armature 82 and the said armature, shaftsprings 72 and 73, rotary ofi' normal spring 67 and its resting contact (this rotary ofl normal spring is not shifted until the. eleventh rotary step), armature 80 and its resting contact, armature and its workingcontact, armature 101 and its restingcontact,

andthe winding of therotary magnet-Gl to battery by way of the common relay 103. "When the above circuitis closed the rotary magnet 61 is energized and rotates .the switch shaftto advanceithe wipers 130.132, inclusive, into engagement with the first set of bank contacts in the ninth level. In operating, the rotary I nagnet breaks the in terrupter contact at itsarmature 88 which is included in thelocking circuit of the test relay 57, and this: relay is accordingly deenergized'tobreak-the circuit of the rotary magnet, which then deenergizes also and again closes its interrupter contact. The operation now depends upon whether, zlZhS first trunk linerin the ninth level lis busy or idle. Ifthis trunk lineis busy,-.the:test contact with which the test wiper 131 is in engagement will have a ground potential uponit and since the said test wiperlias been-connectedto the test.relay.57 by the operation ofthe. slowiactingrelay 58 (relay 58 is energized in parallel with the rotary magnet, as before explained), th'etest relay 57 will again be energized andwillrreestab- .lish its lockingcircuitwand the energizing circuit of the rotary magnet 61. In this .manner the wipers are'advanced into engagement with the'second set of contacts,

and the same operation isrepeatedi rapidly until an idletrunk lineis reached. Assuming that the trunk line shown in the drawing 1 and comprising conductors 14:5 and 146 and with the same results.

Since di- The desired connection has now been established. Ringing current is automatically projected out over the trunk line the same asin the case of the called local line and the ring down drop or other signalling device at the manual switchboard is operated in the usual manner. hen the operator plugs in to answer the call the ring out off relay 56 is operated, disconnects the ringing current, and completes the talking connec tion. The connection to the desired local station in the main exchange may be completed by the operator through the medium of any suitable means which need not be explained herein.

The operation of the restricted service devices may now be explained a little more fully. It will have been noted that the circuit of the rotary magnet 61 when the same was used in the trunk hunting operation includes armature 82 of the discriminating relay 53. This relay is energized over the discriminating trunk conductor 106 at the beginning of the vertical movement of the switch, provided that the calling subscriber is a subscriber in class No. 8, for when any subscriber in this class calls the diseriminat ing trunk conductor will be connected with solid ground by the extra. wiper of the calling line switch. However, if a subscriber in class No. 2 is calling, ground will be connected to thediscriminating trunk conduc tor through 500 ohms resistance'and the discriminating relay 53 consequently will not energize. if It follows therefore, that resist ance 104 is not shortcircuited and when the rotary magnet circuit is completed this re sistance is included in the circuit. As a result, neither the rotary magnet 61 nor the slow acting relay 58 which is connected in parallel therewith is energized, and the test relay 57 being now in operated position, the calling subscriber is given a busy signal to warn him that the desired connection cannot be obtained. The result obtained by the subscribers in class No. 1 when calling for main oilice trunk lines will obviously be the same as described above for the subscribers of class No. 2.

Th operation of the selector connector repeater D when used for trunking to the second private automatic exchange is the same as in the case just described in so far as the selection of an idle Itrunk line is concerned, but since the connection in the private automatic exchange must b completed automatically the circuits of the switch D are altered suitably in order to permit the switch to operate as a repeater for the purpose of repeating impulses over the selected trunk line. The operations which take place when the connection is extended to the second private automatic exchange will now be briefly explained. to the second P. A. X. terminate in the tenth Since the trunk lines extending level, the digit to be called is the digit 0. Assuming the same conditions as before, the calling subscriber being the subscriber at substation A, when the calling device is'operated for this digit the wipers of the selector connector repeater D will be raised to the tenth level. By this operation the ninth level shaft springs are closed as in the previous case and also the tenth level shaft springs 68 and 69 are closed. By the closure of the tenth level shaft springs a circuit is completed for relay in series with the upper winding of the ring cut off relay 56. Both these relays are energized and the latter. relay disconnects the ringing current and locks itself as usual. \Vhen the slow acting relay 52 deenergizes at the end of the vertical movement of the switch the automatic trunk selecting movement is initiated as before explained, and the switch wipers ar rotated step by step under control of the test relay 57 in search of an idle trunk line. Assuming that the first idle trunk line is the trunk line comprising conductors 147 and 148, when the wipers 130- 132, inclusive, arrive at bank contacts 189- 141, inclusive, the test wiper 181 will find no ground potential on test contact 140 and the rotation of the switch will cease. The switching relay 59 is now energized in the usual manner and the connection with the trunk line is thereby completed. Since relay is now in operated position the :two windings of the impedance coil 54 will be bridged across the trunk line in an obvious manner and a circuit will be completed for energizing the line relay of the connector switch in which the trunk line terminates at the second private automatic exchange. The calling subscriber may now operate his dial in accordance with the digits in the desired number at the second P. A. X. lVheu the first digit is called th line relay 50 is deenergized a plurality of times and at each deenergization said line relay opens the bridge across the trunk line conductors 147 and 148 at its armature 78, thus repeating the interruptions produced by the calling device at th calling substation into the circuit of the line relay of the connector switch at the No. 2 P. A. X. At the same time line relay 50 sends a series of impulses through the slow acting relay 58, and this relay completes the bridge across the trunk line conductors 147 and 148 over a direct path which excludes the windings of the impedance coil 54 but includes the arma ture 78 of relay 50. This circuit change is accomplished at armature 92 of relay 5S and will be understood without difficulty. The connector at the No. 2 P. A. X. is operated in the usual manner in response to the receivedimpulses to select a desired level and when the next digit is called it is further operated to complete the desired connection.

These operations are well understood and willrequir no further explanation. It will be: clear that the trunk linesleadingto the second P. A. X. may terminate in line switches instead of incomingficonnectors if desired, or if the second P. A. X..is of large size they may terminate in selector switches. the exact trunking arrangement used being unimportant.

With reference to the restricted service feature, it will be understood that subscribers in classNo. 2 can also connect with trunk lines on the 'tenth level, for when the switch is raised to this level relay 55 short circuits resistance and thus permits the discriminating relay 53to be operated by a 500 ohinground-onthe discriminating trunk.

Although not shown in the drawing it will be understood of course that suitable arrangements are provided tor handling in coming calls from the manual main exchange and from the second private branch exchange to the, private branch exchange under consideration. The trunk lines shown may be madetwo-wayby the use of well known expedients, or separate trunk lines may be provided which terminate in incoming connectors at the-first private automatic exchange, the banks ofthese incoming connectors'being providedwith a multiple of all the local'l'ines. But since nothing new is involvedin these provisions for handling im coming tratiic the circuits have not ben shown and need not be consideredherein.

I will now explain briefly a'feat'ure which consists in tl'ieprovis'ionof means for regis tering the total number of calls which are attempted to be established over a group of trunk lines and which fail'because all of the trunk lines in the group are busy. The means for accomplishing this is shown at the lower right hand corner of the drawing and comprises the meter M andrelay 200 together with suitable circuitarrangements whereby the relay is operated at suitable timesto con'trolflthe meter. t will be as sumed that this metering arrangement is applied to the group of trunk lines extending to the manual main exchange and which terminate in the ninth level of the selector connector repeaters. Assun'iing that there are 7 of these trunk lines in thegroup they will be assigned to the first 7 contact sets in the bank. This is indicated clearly in the drawing which shows-the ten test con tacts of the ninth level and-their circuit connections. The eighth and ninth test con tacts areconnected in multiple to the relay 200 while the last test contact ispermanent-ly grounded. Assume now that a call is attempted when all of the seven trunk lines are busy, the selector connector repeater D being used toset up the connection. When the trunk hunting movement is initiated the test wiper 131 will find the first seven test to its working contact.

. connection.

contacts grounded and the switch will be rotated past the first seven contactset s in the well understood manner. Since the eighth and ninth test cont-acts are also groundedthrough the winding-of relay 200, the rotary movement willbe continued past the eighth and ninth cont-a'ct'sets in the same manner. The tenth contact set is permanently connected to ground and'the switch therefore will not stop at this point either but the rotary movement will continue until the wipers are rotated entirely off the bank. This occurs on the eleventh rotary step at which timethe rotary cam 66 shifts the rotary oil normal spring 67 from its resting By this operation the circuit ofthe rotary magnet 61 is broken and the rotation of the switch is stopper. When the contact spring 67 comes into engagement with its working contact an energizing circuit is completed for the test relay 57 and this relay is held'up until the connection is released. As soon as the slow acting relay 58 deenergizes. the subscriber is given an audible busy signal in the manner previously explained. The ul'isucc'essful trunk hunting movement described above causes the meter M to be operatedonce'to register the unsuccessful attempt at setting up a When the test wiper 131 passes over the eighth and ninth test contactsthe test relay ofenergizes in series with the me ter controlrelay 200. This relay is slow act ing and pulls up its armature once in response to the two current impulses received in order to operate the meter M. Since the test wiper 1.31 moves oil the meter control. Contacts, thereby permitting the meter to re store any other similar switch which is hunting for anidle trunk will also operate the m'et'er'hl as it passes overthe meter control contacts even though th first of the switches has not yet released. It will be seen that by means of a metering arrangement ofthis kind lost calls due to insutiicient trunking capacity which might otherwisenot be noticed will be called to the attention of the management, and. the scheme is thus oi great assistance in keeping acheck on traiiic conditions, I

Having described my invention. what I consider to be new and desire to have pro tectedby Letters Patent will be pointed out in the appended claims.

llhat I claim as my invention is:

1. In a telephone system, automatic switches for connecting calling and called lines,' release magnets for said switches, a relay connected in circuit with all of said magnets, and a meter controlled by said relay for registeringthe total number of completed connections in the system.

2. In 'a telephone system, automatic switches for connecting calling and called lines, operating and release magnets in said switches, a relay connected in circuit with all said operating magnets, a second relay connected in circuit with all said release magnets, and a meter controlled jointly by said relays for registering the total number of completed connections in the system.

3. In a telephone system, automatic switches for connecting calling and called lines, operating and release magnets in said switches, a relay connected in circuit with all said operating magnets, a second relay connected in circuit with all said release magnets, a meter controlled jointly by said relays for registering the total number of completed connections in the system, and circuit connections such that the meter will be actuated when the first relay is energized alone but will not. be actuated when said relays are energized together.

l. In a telephone system, a group of trunk lines, automatic switches having access to said trunk lines for establishing connections, a meter, and means for actuating said meter whenever a connection is attempted via said group of trunk lines and all the trunk lines are found to be busy, said means including a test contact, a meter control relay, and circuit connections whereby a busy potential is applied to said test contact through said relay.

5. In a telephone system, a group of trunk lines, an automatic switch, means for operating said switch to select and connect with an idle one of said trunk lines, an all trunk busy relay energized only while said switch is in motion, and a meter controlled by said relay.

6. In a telephone system, a group of trunk lines, an automatic switch, means for operating the same to select and connect with an idle one of said trunk lines, means for continuing the operation of said switch automatically for an interval it all said trunk lines are busy, a meter, and means for automatically actuating said meter during said interval.

7. In a telephone system, a group of trunk lines, an automatic switch, means for operating the same to select and connect with an idle one of said trunk lines, means for continuing the operation of said switch auto matically for an interval if all said trunk lines are busy, a relay energized only during the continued movement of said switch, and a meter controlled by said relay.

8. In a telephone system, a group of trunk lines, an automatic switch, means for operating the same to select and connect with an idle one of said trunk lines, a test relay in said switch controlling the trunk selection, a second relay energized in series with said test relay provided all said trunk lines are busy, and a meter controlled by said second relay.

9. In a telephone system, an automatic switch for connecting calling and called lines, a release magnet for said switch, a relay connected in circuit with said magnet, and a meter controlled by said relay to register the number of connections established by said switch.

10. In a telephone system, automatic switches for connecting calling and called lines, release magnets for said switches, a meter for registering the total number of connections, and suitable circuit arrangements for operating said meter whenever any one of said release magnets is operated.

11. In a telephone system, automatic switches each having primary and secondary connecting movements, means for operating and releasing said switches, a meter, and circuit connections for operating said meter whenever any one of said switches is fully operated and released, but not when a switch is released after being only partially operated.

12. In a telephone system, automatic switches each having primary and secondary connecting movements, means for operating and releasing said switches, a meter, means for operating said meter whenever any one of said switches is released after having been operated in both its movements, and means for preventing the operation of said meter when a switch is released after having been operated in its primary movement only.

13. In a telephone system, an automatic switch having operating and release mag nets, circuit connections for energizing said magnets in quick succession or for energizing the release magnet a relatively long interval after the operating magnet, a meter, and suitable circuit connections for operating said meter only in case the said release magnet is energized a relatively long interval after the operating magnet.

let. In a telephone system, an automatic switch having operating and release magnets, circuit connections for energizing said magnets in quick succession or for energizing the release magnet a relatively long interval after the operating magnet, a meter, circuit connections for operating said meter when the said release magnet is energized, and a device for preventing the operation of the meter in case the energization of the re lease magnet follows immediately after the energization of the operating magnet.

15. In a telephone system, an automatic switch, a group of trunk lines, means for operating said switch to select and connect with an idle one of said trunk lines, said means including test contacts for said trunk lines, means including other test cont-acts permanently busy for further operating said switch in case all said trunk lines are busy,

of said test contacts being assigned to a group of trunk lines, the last test contact I being an overflow contact, and the intervening contacts assigned for alltrunk busy metering, an all trunk busy meter, and a meter control relay connected to said intervening test contacts.

17. In a telephone system, a selector switch having a row of test contacts, certain of said test contacts being assigned to a group of trunk lines, and another test contact further along in the row being assigned for all trunk busy metering, means for moving the wiper of said selector past all said test contacts in case all of said trunk test contacts are busy, an all trunk busy meter, and circuit connections for operating said meter when the selector wiper moves past the all trunk busy test contact.

18. In a telephone system, a selector switch having a row of test contacts, one of said test contacts being assigned to a working line, and another test contact further along in the row being assigned for metering, means for moving the Wiper of said selector past both said contacts in case theline test contact is busy, a meter, and circuit connections for operating said meterwhen the selector wiper moves past the said meter contact.

19. In an automatic telephone system, a plurality of groups of trunk lines, .a plurality of selector switches for extending calling subscribers lines to idle trunk lines in selected groups, a meter for each group of trunk lines, and circuit connections whereby a plurality of subscribers calling the same group of trunk lines at the same time can each operate the meter associated with the selected group of trunk lines in case all of the trunk lines in such groupare busy.

20. In a telephone system, a plurality of groups of trunk lines, a plurality of selector switches for extending calling subscribers lines to idle trunk lines in selected groups, a meter for each group of trunk lines, and circuit arrangements effective in case all the trunk lines in a selected group are busy for operating the meter associated with such group once for each of a plurality of selectors whichare operated simultaneously in an attempt to connect with a trunk line in the busy group.

21. I11 a telephonesystem, calling lines, a group of tru'nklines accessible to said calling lines, selector switches for connecting said calling lines to idle trunks of said group, a meter for registering the number of calls which are lost due to all trunks of the group being in use, circuit arrangements for operating said meter immediately when the first of a plurality of calls are lost, and means for again operating said meterif another call is' lost prior to the release of the first attempted connection.

Signed by me at Chicago, Cook County, Illinois, this 9th day of September, 1920.

ARTHUR J. RAY. 

